Without limiting the scope of the invention, its background is described in connection with vibration isolation devices for aircraft.
One example is U.S. Pat. No. 8,888,079, issued to Smith et al., entitled “Apparatus for Improved Vibration Isolation”, which describes a vibration isolation device having an upper housing defining an upper fluid chamber, a lower housing defining a lower fluid chamber, a piston resiliently disposed within the upper housing and the lower housing, a tuning passage defined by the piston, for providing fluid communication between the upper fluid chamber and the lower fluid chamber, a tuning fluid disposed within the tuning passage, the upper fluid chamber, and the lower fluid chamber. A reservoir in fluid communication with the upper fluid chamber for providing pressurization control of the vibration isolation device. An expanded accumulator region for providing increased pressure retention during maintenance and operation of the vibration isolation device.
Another example is taught in U.S. Pat. No. 9,279,741, issued to Lee et al., entitled “Mechanically Optimized Liquid Inertia Vibration Eliminator and Aircraft Pylon System”, which describes a vibration isolation device includes an upper housing and a lower housing; an upper reservoir housing defining an upper fluid chamber; a lower reservoir housing defining a lower fluid chamber; a piston spindle resiliently coupled to the upper housing with an upper elastomer member, the piston spindle being resiliently coupled to the lower housing with a lower elastomer member; an elongated portion having a tuning passage; and a tuning fluid disposed there within. The vibration isolation device cancels vibratory forces at an isolation frequency. The vibration isolation device is utilized in a pylon system for mounting a transmission in an aircraft. The vibration isolation device is located between a pylon structure and a roof structure. The isolator includes a spherical bearing assembly that is located near a waterline location of a rotational axis of a drive shaft.
Another example is taught in U.S. Pat. No. 9,669,922, issued to Griffin, entitled “Flow Restriction System for Regulating Dynamic Pressure Loss”, which describes a vibration control system includes an outer housing, an inner housing carried within the outer housing, a fluid passage extending through the inner housing and in fluid communication with a first fluid reservoir and a second fluid reservoir on opposing sides of the inner housing, and a gas extraction system. The gas extraction system includes a gas reservoir in fluid communication with the first fluid reservoir, a removable cap secured to the outer housing, a lid removably attached to the cap, and a plurality of conduits extending through cap and lid and configured to provide fluid and gas communication between the first reservoir and the gas reservoir.
Another example is taught in U.S. Pat. No. 9,777,788, issued to Lee et al., entitled “Rotorcraft Vibration Suppression System in a Four Corner Pylon Mount Configuration”, in which the vibration suppression system includes a vibration isolation device located in each corner in a four corner pylon mount structural assembly. The combination of four vibration isolation devices, two being forward of the transmission, and two being aft of the transmission, collectively are effective at isolating main rotor vertical shear, pitch moment, as well as roll moment induced vibrations. Each opposing pair of vibration isolation devices can efficiently react against the moment oscillations because the moment can be decomposed into two antagonistic vertical oscillations at each vibration isolation device. A pylon structure extends between a pair of vibration isolation devices thereby allowing the vibration isolation devices to be spaced a away from a vibrating body to provide increased control.
The foregoing patents are hereby incorporated by reference in their entirety.